The alloying additions for manganese alloying of metal alloys, containing manganese as a basic alloying element and aluminum as a base, are well known. Increase of alloying element content in alloying addition is a topical problem, as it permits to use less material for alloying. When using the alloying addition for alloy production, the alloying addition should provide high Mn dissolution rate and high Mn recovery degree in the alloy and, eventually, should guarantee the required content of Mn in the final product.
Alloying additions containing Mn are known as master alloys, in the form of Al—Mn alloy, as well as in the form of pressed briquettes and tablets.
Well known is the method for producing of alloying addition in the form of Mn and Al briquette for alloying of aluminum alloys (SU 1772194, A. N. Malenkikh et al., Int. Cl. C22B 9/10, 30.10.1992). The method includes pressing the mixture of crushed Mn or Mn compound (55-65%), refining flux (5-9%) and crushed in chips aluminum or Al alloys (30-36%). The alloying addition produced this way has the following deficiencies: low content of Mn, low Mn recovery degree, considerable losses of Mn and Al, high content of hydrogen and Na, oxides and other non-metallic impurities, which contributes to undesirable slag formation.
Well known are the alloying additions containing Mn and Al, in the form of pressed tablets (hereafter referred to as “tablets”) Mn75, Mn80. The Mn80 tablets are produced by pressing of powder mixture containing 80% Mn and 20% Al and sometimes fluxes (MgCl, NaCl, etc.) The Mn80 tablets are applicable for alloying aluminum alloys with Mn and ensure the high Mn dissolution rate in aluminum melt and the high Mn content in the finished alloy. The shortcoming of the Mn80 tablets is the low recovery degree of Mn in the alloy and increased slag formation during alloying, caused by the high content of oxygen (up to 2%) in the alloy in the form of Mn oxides and hydroxides and Al oxides available on the surface of metal particles in the briquette. The slag formation causes high impurity and lower quality of final product, increased losses of aluminum, clogging of furnaces, channels and electromagnetic pumps (hereafter referred to as “EMP”), and as a result, the depreciation of equipment. All this, in the aggregate, leads up to the increase of production cost of alloyed Al alloy.
Are also known the master alloys in the form of Al—Mn alloys, for example, master alloy AlMn20 containing 20% Mn and 80% Al, and further created master alloy AlMn60 containing 60% Mn and 40% Al.
The nearest to the present invention technical solution is a known master alloy AlMn60 (EN AM-AlMn60), which contains 40% Al, 60% Mn and other components too, and is made in the form of splatters, according to the Europe Community Standard CEN/TC 132 “Aluminium and aluminium alloys—Master alloys produced by melting—Specifications” (directive No. 97/23/EC), cite EN 575:1995, ratification date Jun. 3, 1995. The known master alloy is produced by a known method, according to which Al is loaded into furnace, melts and is heated to a specified temperature. After that, the temperature being maintained, the rated amount of Mn and other components is added in the melt portion-wise. The obtained melt comes to homogeneous state, is being held during the time and, once the prescribed content of components is reached, the casting of the obtained alloy occurs with cooling, thus forming the splatters (the splatters of the alloy mean the alloy in form of “flake”) of the alloy. The known method includes the heating of Al up to 1300° C., and the casting is to be done, after the Mn content in the melt has reached 60%, with forming splatters of the master alloy with thickness of 2-5 mm. This master alloy is used for alloying Al alloys. The master alloy has the crystal structure in which during rapid heating, in the process of alloying, under the temperature in the range of 540-570° C. directed phase transformations arise followed by the volume increase. This creates the internal stresses in the crystal lattice, which break down the master alloy into small particles having size of 100-400μ, thus bringing the master alloy to decomposition and causing Mn dissolution in the melt. The deficiency of the known master alloy AlMn60 is the low content of Mn (not more than 60%) and, as a result, the higher expense of the master alloy for a unit of the final product and consequently the high cost of the master alloy in terms of 1 kg of Mn. Also, this master alloy has the low dissolution rate during alloying.
Thus, no high-performance master alloy for alloying metal alloys with Mn is known from the background art, which master alloy would have high Mn content and would guarantee high Mn dissolution rate in the melt, as well as high Mn recovery degree in the alloy, without producing slag formation which effects negatively the quality of the alloy.
The object of the present invention is to eliminate the above mentioned deficiencies and to create a new high-performance master alloy for Mn alloying of metal alloys and a new method for producing the master alloy, which would guarantee the high content of Mn, high Mn dissolution rate in the melt and high Mn recovery degree in the alloy without slag formation and contamination of metal alloy, when using the master alloy for production of alloys.